1. Field of the Invention
The present invention relates to endoprothesis devices such as vascular stents and, more particularly, to vascular stents that are radially expandable.
2. State of the Art
Vascular stents are prosthetic devices that can be placed inside a lumen to support the lumen and to assure its patency. Stents are frequently implanted within vascular systems to reinforce collapsing, partially occluded, weakened, or abnormally dilated sections of blood vessels. Stents are widely used in angioplasty procedures which are concerned with the repair and reconstruction of blood vessels. More generally, however, stents can also be used inside the lumen of any physiological conduit including the arteries, veins, bile ducts, urinary tract, alimentary tract, tracheobronchial tree, cerebral aqueduct, and genitourinary system. Stents can also be used inside lumina of animals other than humans.
In one typical procedure for implanting a stent in a blood vessel, the stent is mounted on a balloon-tip catheter which is then slipped through an incision in the vessel wall and worked along the length of the vessel until a position is reached where the stent bridges a diseased or narrowed section of the vessel. Then the balloon on the balloon-tip catheter is inflated to radially expand the stent in place against the inside wall of the vessel while the vessel is dilated by the inflated balloon.
In practice, stents should be as atraumatic as possible to vessels and blood cells. As suggested by the above-identified application, one manner for reducing trauma is to form stents from biocompatible material and to minimize the quantity of material used. Trauma also can be reduced by devising stents that have exterior surfaces that are free from tines or sharp edges that might damage the wall of a blood vessel that surrounds the stent. Further trauma can be reduced by devising stents that, as again suggested by the above-identified application, have sufficient flexibility in their compressed state to conform to the tortuous paths of vessels through which the stent is inserted while being generally rigid in their expanded state.